A thin-film photoelectric conversion device of a mechanical stack type in the past includes, for example, a photoelectric conversion module in which thin-film semiconductor layers are formed as photoelectric conversion layers on a substrate having a transmissive electrode formed thereon and a photoelectric conversion module in which thin-film semiconductor layers are formed as photoelectric conversion elements on a substrate having a reflective metal electrode layer formed thereon. With the two substrates opposed to each other, the photoelectric conversion modules are bonded such that surfaces of the respective substrates on which the thin-film semiconductor layers are not formed are arranged on the outer side. Outputs are separately extracted from the photoelectric conversion modules. In each of the photoelectric conversion modules, in a state in which a plurality of photoelectric conversion elements processed in a stripe shape are arranged with the elements adjacent to each other spaced a predetermined distance apart from each other, the photoelectric conversion layers adjacent to each other are formed to be electrically connected in series while being electrically separated.
In such a photoelectric conversion device of the mechanical stack type, the photoelectric conversion modules to be laminated are respectively formed on independent substrates. Therefore, there is an advantage that processes of formation of the respective photoelectric conversion modules are simplified and manufacturing yield is improved. There is also an advantage that, even if one of the substrates causes a failure during manufacturing, the remaining substrate can be stacked on another substrate and used. On the other hand, in a laminated thin-film photoelectric conversion device formed by continuously forming films on a single substrate, performance is higher than that of the mechanical stack type. However, when a failure occurs in a part of layers, the entire photoelectric conversion device cannot be reused and manufacturing yield is deteriorated.
In the thin-film photoelectric conversion device of the mechanical stack type, to improve efficiency, a band gap of the photoelectric conversion layers formed on the substrate on a light incident side is set wider than a band gap of the photoelectric conversion layers formed on the other substrate. Consequently, light having high energy (short wavelength) is absorbed by the photoelectric conversion elements formed on the substrate on the light incident side and light transmitted through the photoelectric conversion elements is absorbed by the photoelectric conversion elements formed on the other substrate. Therefore, it is possible to efficiently use the light.